Nitriding



Patented July '10, 1934 f UNITED TES John J. Brooklyn, n. I, assi'gn'or to Electra. Metallurgical Company, a corporation of :West

' Virginia Application February 2c, 1930, Serial No. 431,642

'Myinvention relates to the production of nitride cases on ferrous mate ls by heating the materials in the presenceof ni ding agen s, and it is the main object of my invention to intensify or accelerate the production of such Thin, hard, wear-resistant. cases on ferrous alloys are useful as wearing surfaces for machine parts. The cases may be producedby nitriding, i. e.-, by heating the alloys in the presence of nitriding agents to temperatures below the-nitride eutectoid temperature at about 600 C. In

a nitriding gas, such as ammonia, a treatment of 12 to 20 hoursis required to produce'the cases, the treating time usually being longer when lower temperatures are used than when higher temperatures are used. The hard, wear-resistant cases are usually produced by heating in an atmosphere of ammonia to about 460 C. to 580 0., the treated alloy containing a promoting agent, such as aluminum'or vanadium, which promotes the formation of the hardgwear-resistant coating at .thesetemperatures. By far .the mostextensive use of invention is in connection with the production of hard, wearresistant coatings and the invention will be described with reierencethereto.

It has been found that the action of nitriding agents is intensified when organic .compolmds containingnitrogen, and especially the closed carbon chain amino compounds, are present. For example, a tntride case of a given thickness can be produced in less time by-h'eating steel in a mixture of. ammonia and a closed carbon chain amine than by heating the steel under conditionsin ammonia which does not contain the amine.

-As illustrative of my invention, a specimen of ferrous alloy containing about 95.5% iron 1% aluminum, and small amounts of phosphorus, sulphur, rue, ..,silicor 1,. nickel, chromium,

molybdenum and carbonwas' ila'oed in a closed container. Ammonia was le d aniline which was heatedto a temperature just below its boiling point to increase itsvapor pressure. The entrapped in the container was displaced by the mixture-of ammonia and aniline .yapo and the container and its contents were heated to 460 C. for thours whilst a slow cm rent of the gas was passedinto the containen: A thin, uniform, wear-resistant case having a hardness corresponding to ,about' 1 000 Brinell was produced on the A ilar hard, wear resistant-case was produced another specimen of the same alloybyheating for '16} hours in ammonia but-without themes- (01. its-F16) ence of aniline yapor. a treatment in am- -monia. and without the aniline no appreciable hardness was ,produced by heating the alloy 4 such as oxnapthylamine or other carboncompounds of the type R. M. in which R represents one or. more aliphatic or closed carbon chain radicals and M represents one or more radicals composed of nitrogen or nitrogen and hydrogen linked to a carbon containing radical.

'Any appreciable amount of the organic amino .compotmd in conjunction with a nitriding agent is suflicient to-produce acceleration. The pre- Ierred amount to be used with a given alloy under vgiven conditions may. be determined by experi- 1 celeratonwhich is introduced .with the nitriding agent. 1

Although lhave given only arew specific examples of accelerators and only one example of a nitriding agent, it is evident that other sub- =15 ment' for'each particular case but theinvention stances of the classes described may be used and modifications of the describedmethod may be made without departing from my invention. Therefore, I do not wish to be understood as imposing limitations on my invention except such as are imposed by the prior art and by the annexed claims.

I claim: a

1,. The method ferrous materials which comprises heating the .material at nin'iding temperatures below the eutectoid at about 600 C. in the presence of am-.-' monia. and at least one of the following; aniline, phenylene dame, u-nanhthylaminejthe amr'nonia forming a predominating proportion .of

said'n ediumia 2. Method of accelerating the production or, nitride cases on ferrous materials by heatingthe materials in the presence of ammonia which comprises eifecting said nitriding in the presence of an accelerating agent consisting of an aromatic of'producing nitride cases on -primary amine chosen from the group comprisaniline, phenylene diamine, ,a-naphthylaminef said accelerating agent being present in matev rially less amount than the ammonia.-

4. Nitriding medium comprising ammonia and an aromatic primary amine chosen from the group: .monoamino anddiamine phenyl and.

naphthyl primary amines? the ammonia forming a. predominating proportion of said medium.

5. Nitriding medium comprising ammonia and at least one of the following: aniline, phenylene diamine, a-naphthylamine; the ammonia forming a pr'epon'derating proportion of said medium.

correctiontherein that. the same may conform to 1 6. A gaseous nitriding medium consisting of ammonia and a minor proportion of aniline.

7. The method of producing'nitride cases on ferrous materials which c mprises passing a,

stream of ammonia in conta t with an aromatic primary amine chosen from the groupcompris-y Patent No. 1,965,798.

' -.It is hereby numbered patent phenyiene diamine,

;Certifi ca te of Correct hi1 I Y Jo N J. mink ertiiied that errorfappears in" the printed specification of the above requiring correction as follows :12

1,9eiiizbs ing monoamino anddiamino phenyl and naphthyl primary amines, whereby a mixture of ammonia and amine isformed, and heating. the ferrous material at nitriding temperatures below the nitride eutectoid at about 600 (2. in the presence of the mixture.

8. The method of producing nitride cases on ferrous materials which comprises passing a stream of ammonia in contact with an aromatic primary amine chosen from" the group: aniline,"

phenylene diamine, a-naphthylamine; whereby a mixture of ammonia and amine is formed; and heating the ferrous material at nitriding', temperatures below the nitride eutectoid at about 600 C. in the presenceofthe mixture. 1

9. The method of producing nitridecasespn ferrous materials which comprises passing "a" stream of ammonia in contact with an aromatic primary amine chosen from the group: aniline, a-naphthylamine, which amine, is ata temperature near its boiling point,

wherebya mixture of ammonia and amine is nitriding temperatures below the nitride eutec formed: and heating-the ferrous material at Joint J. EGAN. 3 1

July 10, 1934,

.age 1,'line 65 for foxn'a'pthylamine reaJh-mphthylamine; and that the said Letters Patent should beread with I this therecord of the Pat nt ,Signedandfsealed 7th day of August, 1934. I

j 'LEisLIE-FnAfzEa- Actingof Patents.

aniline, phenylene diamine, ,a-naphthylaminef said accelerating agent being present in matev rially less amount than the ammonia.-

4. Nitriding medium comprising ammonia and an aromatic primary amine chosen from the group: .monoamino anddiamine phenyl and.

naphthyl primary amines? the ammonia forming a. predominating proportion of said medium.

5. Nitriding medium comprising ammonia and at least one of the following: aniline, phenylene diamine, a-naphthylamine; the ammonia forming a pr'epon'derating proportion of said medium.

correctiontherein that. the same may conform to 1 6. A gaseous nitriding medium consisting of ammonia and a minor proportion of aniline.

7. The method of producing'nitride cases on ferrous materials which c mprises passing a,

stream of ammonia in conta t with an aromatic primary amine chosen from the groupcompris-y Patent No. 1,965,798.

' -.It is hereby numbered patent phenyiene diamine,

;Certifi ca te of Correct hi1 I Y Jo N J. mink ertiiied that errorfappears in" the printed specification of the above requiring correction as follows :12

1,9eiiizbs ing monoamino anddiamino phenyl and naphthyl primary amines, whereby a mixture of ammonia and amine isformed, and heating. the ferrous material at nitriding temperatures below the nitride eutectoid at about 600 (2. in the presence of the mixture.

8. The method of producing nitride cases on ferrous materials which comprises passing a stream of ammonia in contact with an aromatic primary amine chosen from" the group: aniline,"

phenylene diamine, a-naphthylamine; whereby a mixture of ammonia and amine is formed; and heating the ferrous material at nitriding', temperatures below the nitride eutectoid at about 600 C. in the presenceofthe mixture. 1

9. The method of producing nitridecasespn ferrous materials which comprises passing "a" stream of ammonia in contact with an aromatic primary amine chosen from the group: aniline, a-naphthylamine, which amine, is ata temperature near its boiling point,

wherebya mixture of ammonia and amine is nitriding temperatures below the nitride eutec formed: and heating-the ferrous material at Joint J. EGAN. 3 1

July 10, 1934,

.age 1,'line 65 for foxn'a'pthylamine reaJh-mphthylamine; and that the said Letters Patent should beread with I this therecord of the Pat nt ,Signedandfsealed 7th day of August, 1934. I

j 'LEisLIE-FnAfzEa- Actingof Patents. 

